Hypertrophic pyloric stenosis (HPS) causes a functional gastric outlet obstruction as a result of hypertrophy and hyperplasia of the muscular layers of the pylorus. In infants, hypertrophic pyloric stenosis is the most common cause of gastric outlet obstruction and the most common surgical cause of vomiting.
Signs and symptoms
Features of the history in infants with hypertrophic pyloric stenosis are as follows:
Typical presentation is onset of initially nonbloody, usually nonbilious vomiting at 4-8 weeks of age
Although vomiting may initially be infrequent, over several days it becomes more predictable, occurring at nearly every feeding
Vomiting intensity also increases until pathognomonic projectile vomiting ensues
Slight hematemesis of either bright-red flecks or a coffee-ground appearance is sometimes observed
Patients are usually not ill-looking or febrile; the baby in the early stage of the disease remains hungry and sucks vigorously after episodes of vomiting
Prolonged delay in diagnosis can lead to dehydration, poor weight gain, malnutrition, metabolic alterations, and lethargy
Parents often report trying several different baby formulas because they (or their physicians) assume vomiting is due to intolerance
Careful physical examination provides a definitive diagnosis for most infants with hypertrophic pyloric stenosis. The diagnosis is easily made if the presenting clinical features are typical, with projectile vomiting, visible peristalsis, and a palpable pyloric tumor. Early in the course of the disease, however, some of the classic signs may be absent.
An enlarged pylorus, classically described as an “olive,” can be palpated in the right upper quadrant or epigastrium of the abdomen in 60-80% of infants.
Assessment of the pylorus requires the following:
The patient must be calm and cooperative; a pacifier or small amount of dextrose water may help
If the stomach is distended, aspiration using a nasogastric tube is necessary
With the infant supine and the examiner on the child’s left side, gently palpate the liver edge near the xiphoid process, then displace the liver superiorly; downward palpation should reveal the pyloric olive just on or to the right of the midline
To be assured of the diagnosis, the physician should be able to roll the pylorus beneath the examining finger
The tumor (mass) is best felt after vomiting or during, or at the end of, feeding
When diagnosis is delayed, the infant may develop severe constipation associated with signs of dehydration, malnutrition, lethargy, and shock.
See Clinical Presentation for more detail.
Serum electrolytes should be measured to document adequacy of fluid resuscitation and correction of electrolyte imbalances before surgical repair. The classic biochemical abnormality in hypertrophic pyloric stenosis is hypochloremic, hypokalemic metabolic alkalosis.
The criterion standard imaging technique for diagnosing hypertrophic pyloric stenosis
Muscle wall thickness 3 mm or greater and pyloric channel length 14 mm or greater are considered abnormal in infants younger than 30 days
Barium upper GI study
Effective when ultrasonography is not diagnostic
Should demonstrate an elongated pylorus with antral indentation from the hypertrophied muscle
May show the “double track” sign when thin tracks of barium are compressed between thickened pyloric mucosa or the “shoulder” sign when barium collects in the dilated prepyloric antrum
After upper GI barium study, irrigating and removing any residual barium from the stomach is advisable to avoid aspiration
Reserved for patients with atypical clinical signs when ultrasonography and UGI studies are nondiagnostic
See Workup for more detail.
Hypertrophic pyloric stenosis is the most common condition requiring surgery in infancy. Correction of an associated fluid and electrolytes disturbances is vital prior to general anesthesia induction.
Surgical repair of hypertrophic pyloric stenosis is fairly straightforward and without many complications. However, properly preparing the infant is vitally important.
Directed at correcting the fluid deficiency and electrolyte imbalance
Base fluid resuscitation on the infant’s degree of dehydration
Most infants can have their fluid status corrected within 24 hours; however, severely dehydrated children sometimes require several days for correction
If necessary, administer an initial fluid bolus of 10 mL/kg with lactated Ringer solution or 0.45 isotonic sodium chloride solution
Continue IV therapy at an initial rate of 1.25-2 times the normal maintenance rate until adequate fluid status is achieved
Adequate amounts of both chloride and potassium are necessary to correct metabolic alkalosis
Unless renal insufficiency is a concern, initially add 2-4 mEq of KCl per 100 mL of IV fluid
Urine output and serial electrolyte determinations are performed during resuscitation
Correction of serum chloride level to 90 mEq/L or greater is usually adequate to proceed with surgical intervention
Before induction of anesthesia, aspirate the infant’s stomach with a large-caliber suction tube to remove any residual gastric fluid or barium; saline irrigation is occasionally necessary to remove a large quantity of barium
Ramstedt pyloromyotomy remains the standard procedure of choice
The usual approach is via a right upper quadrant transverse incision that splits the rectus muscle and fascia
Laparoscopic pyloromyotomy may also be used
Endoscopic pyloromyotomy is a simple procedure and can be performed as an outpatient procedure
Endoscopic balloon dilatation of hypertrophic pyloric stenosis after failed pyloromyotomy can be used
A supraumbilical curvilinear approach has gained popularity with good cosmetic results.
Continue IV maintenance fluid until the infant is able to tolerate enteral feedings
In most instances, feedings can begin within 8 hours following surgery
Graded feedings can usually be initiated every 3 hours, starting with Pedialyte and progressing to full-strength formula
Schedules that advance the volume of feeds more quickly or those that begin with ad lib feeds are associated with more frequent episodes of vomiting but do not increase morbidity and actually may decrease the time to hospital discharge
Addition of an H2 receptor blocker sometimes can be beneficial
Treat persistent vomiting expectantly because it usually resolves within 1-2 days
Avoid the temptation to repeat ultrasonography or upper GI barium study; these invariably demonstrate a deformed pylorus, and results are difficult to interpret